Epitalon: A Synthetic Tetrapeptide and the State of Its Evidence

Epitalon — also transliterated epithalon or epithalone — is a synthetic tetrapeptide with the sequence Ala-Glu-Asp-Gly. It is short, chemically simple, and surrounded by a literature that requires unusually careful reading.

Identity, and the several names

Epithalon is a tetrapeptide: Ala-Glu-Asp-Gly, written AEDG in one-letter code. Formula C14H22N4O9, molecular mass 390.35 g/mol, CAS 307297-39-8.

It appears in the literature and in the market under several spellings — Epithalon, Epitalon, Epithalone, and as “AEDG peptide” — which is worth knowing when searching, because the same molecule is indexed under all of them. The registry number is the unambiguous identifier.

At four residues it is one of the smallest compounds in this category, and that has consequences that are entirely practical rather than theoretical.

Origin

Epitalon was developed as a synthetic counterpart to epithalamin, a peptide preparation extracted from bovine pineal gland. Extract-derived preparations are heterogeneous by nature, and one motivation for producing a defined synthetic sequence was to have a single characterised molecule to work with. The two are not interchangeable in the literature, and papers on epithalamin should not be cited as evidence about epitalon.

Why a tetrapeptide is easier to verify than a large peptide

Analytical confidence scales inversely with chain length, and Epithalon sits at the favourable end of that.

• Fewer synthesis cycles. Four residues means roughly four coupling steps rather than thirty-nine. There is far less opportunity for a deletion sequence, which is the impurity class a purity percentage most easily hides in a long peptide.
• A simple mass spectrum. At 390 Da the target peak is unambiguous, and a deletion of any single residue is a proportionally enormous mass change — losing the glycine alone drops 57 Da, nearly 15% of the molecule. Nothing subtle can hide.
• Short retention. A small, highly polar peptide elutes early on a reverse-phase column, which separates it cleanly from most hydrophobic process impurities.

So for this compound, a certificate reporting observed mass against theoretical mass is unusually strong evidence. Compare that with the situation for a 39-residue peptide, where the same document means considerably less — see where peptide impurities come from.

The one liability the sequence does have

Look at the composition: alanine, glutamate, aspartate, glycine. That Asp-Gly pair at the C-terminal end is the classic deamidation and isomerisation motif in peptide chemistry. Aspartate followed by glycine is the most reactive arrangement for succinimide formation, which converts aspartate to isoaspartate — a rearrangement that changes the molecule’s structure while leaving the mass essentially unchanged.

That is the impurity to be aware of here, and it is one a mass measurement will not catch. It is resolved chromatographically or not at all, and it is faster in solution than in the dry state, faster warm than cold, and pH-dependent. Which is the practical argument for keeping the material lyophilised and refrigerated and for not leaving reconstituted solution standing — see storage and stability and limiting repeat vial entry.

There is no methionine, cysteine or tryptophan in the sequence, so unlike many peptides in this catalogue it has no oxidation route available to it. One liability, not several.

Analytical characteristics

At four residues and roughly 390 daltons, epitalon sits near the lower size limit for conventional peptide analysis. Two practical consequences follow.

Short, highly polar sequences retain poorly on standard C18 reversed-phase columns and can elute close to the void volume, where separation from small-molecule impurities is weakest. Analysts often use aqueous-compatible stationary phases or ion-pairing adjustments to address this.

The sequence also contains two acidic residues, making the peptide strongly anionic at neutral pH and highly water-soluble — convenient for reconstitution, but it also means counter-ion content can be a larger proportion of gross weight than for a longer sequence. That is worth accounting for when converting a vial weight into a molar concentration; see net peptide content explained.

What to check on a certificate

Because the molecule is small and simple to make, the sourcing question is less about whether a supplier can produce it and more about whether they can show you what they produced. What to look for: observed mass reported against theoretical, the detection wavelength stated beside the purity figure — a tetrapeptide with no aromatic residues is substantially under-reported at 280 nm and should be measured at 214 nm — and net peptide content, since a small peptide carries proportionally more counter-ion mass than a large one.

That last point is easy to miss and matters here more than usual: on a 390 Da molecule, a trifluoroacetate counter-ion is a large fraction of the total mass. See net peptide content and counter-ions and salt form.

Reading the evidence critically

A researcher evaluating this compound should be aware of several structural features of its literature, because they materially affect how much weight individual findings can carry.

Much of the primary work originates from a small number of affiliated research groups, and a substantial portion was published in Russian-language journals with limited indexing in Western databases. Independent replication outside that network is comparatively sparse. Some frequently cited reports are conference abstracts or review summaries rather than full primary papers with complete methods.

None of this establishes that reported findings are wrong. It does mean that the usual heuristic — a claim repeated across many citations is well supported — fails here, because repeated citation can trace back to a small number of original sources. The indexed literature is at PubMed; searching AEDG peptide surfaces additional records filed under the sequence abbreviation.

The shape of the published record

The published work on Epithalon has a distinctive shape, and recognising it is more useful than any summary of conclusions.

A large share of it originates from a single research group and much of it was published in Russian-language journals, some of it decades ago, with limited independent replication outside that lineage. Study designs are frequently small, and the endpoints reported span a wide range of biological measures rather than converging on one mechanism. No specific receptor has been established for the molecule.

None of that makes the literature worthless — it makes it literature that has to be read with the provenance in view. The practical reading: treat published effect claims as hypotheses generated within one tradition rather than as established findings, and check whether any given result has been reproduced by a group with no connection to the original. For a compound this small and this easy to synthesise, independent replication is cheap; its relative absence is itself informative.

Our note on what binding and potency figures actually measure covers why a reported number without an assay system attached is not comparable to another one.

Products

Product page: Epitalon 10mg. Related background: peptide nomenclature, how to read a certificate of analysis.

ExoLabz supplies compounds for laboratory research use only. Nothing on this page is medical advice or a suggestion of human or veterinary use. Certificates of analysis for each compound are published on this site.